1. Field of the Invention
The present invention relates to an iron-making furnace for obtaining pig iron from iron ore, and particularly relates to a microwave iron-making furnace in which a raw material containing iron ore and coal is heated and melted by microwaves, and the iron ore is reduced to carbon to obtain pig iron.
2. Description of the Related Art
In the steel industry, melted pig iron is usually obtained through blast-furnace iron-making. Specifically, pellets made from iron ore, which is an iron oxide (ferric oxide or ferrous oxide etc.), coke or the like as a carbon source, which is a reducer, and limestone; are loaded into the top of a blast furnace (smelting furnace), hot air (air) is blown in through the tuyere at the bottom of the blast furnace, and an upward flow of hot air is formed in the blast furnace. The falling pellets are heated by the hot air, and the iron ore is reduced by a reaction between the iron ore and the coke. The reduced iron is melted to obtain melted pig iron, which accumulates at the bottom of the blast furnace. After a certain amount of pig iron has accumulated, the pig iron at the bottom of the furnace is taken out through a tapping hole in the bottom of the furnace, and the pig iron flows through a runner channel to be accommodated in a ladle (for example, Japanese Patent Application Kokai Publication No. H11-229007).
However, conventional blast-furnace iron making has had problems in that reducing and melting iron ore requires six hours or more at a temperature of about 1600° C., which is not energy-efficient.
Japanese Patent Application Kokai Publication No. H6-116616 discloses a method for manufacturing an iron powder by using microwaves to heat and reduce iron oxide. In this method for manufacturing an iron powder, iron ore, mill scale, or another such iron oxide that has been crushed; a microwave high-dielectric-constant material as a carbon source whose primary component is coke, char, activated carbon, powdered carbon, or another form of carbon; and calcium carbonate, magnesium carbonate, sodium carbonate, or another carbonate are mixed together. This mixture is irradiated with microwaves to internally heat the carbon source to a temperature in excess of 900° C., and the mixture reacts with the CO2 gas produced by pyrolysis of the carbonate in the mixture to produce CO gas. The iron oxide is reduced by this CO gas to produce an iron powder.
However, the method for manufacturing an iron powder by using microwaves as disclosed in Japanese Patent Application Kokai Publication No. H6-116616 is a method in which iron ore or another iron oxide, coke or another carbon source, and a carbonate are mixed and heated by microwaves, the carbon source is internally heated to a temperature in excess of 900° C., CO gas is produced by a reaction between the carbon source and the CO2 gas resolved from the carbonate in the mixture, and the ion oxide is reduced by this CO gas, but the iron ore, the coke, and the like are not melted. Therefore, with this method, it is only possible to merely manufacture an iron powder, and large amounts of molten pig iron cannot be manufactured efficiently.